Erik ludvig rinman



ERIK LUDVIG- RINMAN, OF DJURSHOLM, SWEDEN.

PROCESS OF PRODUCING SODA CELLULOSE, PARTICULARLY WOOD CELLULOSE.

N 0 Drawing.

To all whom it may concern:

Be it known that I, ERIK LUDVIG RINMAN, a subject of the King of Sweden, residing at Djursholm, in the Kingdom of Sweden, have invented a new and useful Improvement in Processes of Producing Soda Cellulose, Particularly Wood Cellulose, of which the following is a specification.

By the use of the co-called sulfate process it is possible to produce qualities of cellulose which it has heretofore not been possible to obtain by the use of a caustic soda lye free from sulfur. It is well known that cellulose produced by boiling with soda lye free from sulfur is more difiieult to bleach and is colored more yellow than ordinary sulfate cellulose. The present invention, however, re-

the process.

fersto a process by means of which also with the use of caustic soda lye free from sulfur qualities of cellulose are obtained which have quite the same appearance and which are at least equally good as those obtained by means of the sulfate process.

Thepresent process consists principally in this that the caustic soda lye used is treated during the boiling of the material by means of a contact substance furthering reduction. Mercury is especially adapted as such contact material. When carrying out the present process it has proved particularly ad-. vantageous to use as boiling lye a caustic soda lye considerably more diluted than the so-called sulfate lye now ordinarily used. While an ordinary sulfate lye contains about 100 to 120 gr. Na O and Na s in the form of active alkali, there is preferably used ac cording to the present invention a caustic soda lye containing about gr Na O per liter lye.

The said quantity of alkali, and even a greater quantity, being consumed during the boiling, however, a quantity of lye about twice as great as the one now ordinarily used would appear to be necessary for every boiling. It is also possible thus to carry out It is also possible, however, to proceed in such manner that the boiling is begun with the ordinary quantity of fresh lye but with about half the necessary quantity of alkali, that is to say, to use a lye containing about 60 gr. M 0 in the form of free NaOH per liter lye. During the boil- Specification of Letters Patent. t t 0 1;, 21, 1919,

Application filed May 2a, 1918. Serial No. 236,103.

increased over the suitable amount, that is to say, over about 60 gr. Na O per liter lye. The lye thus supplied may be highly concen trated, from 10% NaOH to a higher concentration, if care only be taken that it is supplied in such manner that it is allowed to mix with the other lye before influencing the raw material or the wood.

Cellulose, and particularly wood cellulose, being very little affected by a caustic soda lye of at most 8 per cent. concentration provided that;the temperature is not over 170 (1., it is important, for obtaining agood yield of cellulose, that the process be performed in such manner that the principal extraction of the incrustating substances is made at a temperature of from l-lO C. to 170 C. The time of boiling, however, must then naturally be somewhat lengthened. The lengthening of the time of boiling may be decreased by using artificial pressure during the said extraction, so that the total excess of pressure during the boiling amounts to 10 to 11 kg. per square cm. This additional pressure may suitably be obtained by means of compressed air. The lengthening of the boiling time may be reduced in this manner to amount only to about. half an hour over the usual boiling time.

In order to modify during the boiling the influence of the caustic soda lye it is suitable to provide for the boiling lye always containing a certain quantity of a waste lye from a previous boiling or, still better, a waste liquor freed from lignin substance capable of being precipitated with carbonic acid. This may suitably be effected for instance by producing the caustic sode lye of about 8 per cent. concentration with which the boiling is begun, by dissolving and after ward causticizing soda, for instance soda obtained by dry distillation of waste liquor, in a waste lye from a previous boiling having a specific gravity of from 1.036 to 1.074 and which has been freed from lignin by being treated with carbonic acid, if desired. On the other hand, for producing the necessary quantity of caustic soda lye of a higher concentration, if such lye is used, water may be used as dissolving agent when making the lye, such a solution being more easily filtered.

The extraction from the vegetable raw material, particularly from wood, is facilitated by relieving the wood from the air inclosed in the same before admitting the lye to the wood. This may be effected by drenching the wood with water. It may also be effected by placing the boiler under vacuum before filling the lye into the same. This vacuum may be used for drawing the boiling lye into the boiler.

The mercury used as contact substance during the boiling according to the present invention is not consumed except by wear. It is therefore sufficient once every fourteen days, or even at still longer periods, to give the boiler a very thin coating with mercury, for instance by filling the same with for instance 0.0001 normal I-IgC'l solution, until the mercury has been precipitated on the walls of the boiler. The boiling lye being preferably pumped around in a closed circuit when carrylng out the present process, it is suitable during this pumping to cause the boiling lye to contact with mercury placed as contact substance in suitable manner.

The boiling lye used with the present process is most advantageously regenerated according tothe process described in the U. S. Patent No. 1,196,290 for dry distillation of the waste liquors from the soda cellulose manufacture with strong bases for producing acetone, wood spirit, oils and so forth.

I claim:

1. The process of producing cellulose consisting in boiling the raw material with caustic soda lye and treating the lye during the boiling with a contact substance insoluble in caustic soda lye and furthering reduction.

2. The process of producing cellulose consisting in boiling the raw material with a caustic soda lye and treating the lye during the boiling with mercury.

3. The process of producing cellulose consisting in boiling the raw material with a caustic soda lye free from sulfur, and treating the lye during the boiling with a contact substance insoluble in caustic soda lye and furthering reduction.

4:. The process of producing cellulose consisting in boiling the raw material with a lye containing about 60 gram Na O per liter lye and treating the lye durin the boiling with. a contact substance insolu 1e in caustic soda lye and furthering reduction.

5. The process of producing cellulose, consisting in boiling the raw material with a caustic soda lye, effecting the principal extraction at a temperature of from 140 C. to 17 0 0., and treating the lye during the boiling with a contact substance insoluble incaustic soda lye and furthering reduction.

6. The process of producing cellulose, consisting in boiling the raw material with a caustic soda lye, effecting the principal extraction at a temperature of from 140 C. to 170 (3., subjecting the lye to a pressure exceeding that corresponding to the temperature used, and treating the lye during the boiling with a contact substance insoluble in caustic soda lye and furthering reduction.

7. The process of producing cellulose, consisting in boiling the raw material with a caustic soda lye, containing waste liquor from a previous boiling, efiecting the principal extraction at a temperature of from 140 C. to 17 0 .C., and treating the lye during the boiling with a contact substance insoluble in caustic soda lye and furthering reduction.

8. The process of roducing cellulose, consisting in boiling t e raw material with a caustic soda lye, containing waste liquor from a previous boiling relieved'of lignin, effecting the principal extraction at a temperature of from 140 C. to 170 (1, and treating the lye during the boiling with a contact substance insoluble in caustic soda lye and furthering reduction. a

9. The process of producing cellulose consisting in relieving the raw material from air inclosed in the same, boiling the raw material-with caustic soda lye and treating the lye during the boiling with a contact substance insoluble in caustic soda lye and furthering reduction.

ERIK LUDVIG RINMAN. 

